In mobile communication, a mobile station sends out random access control signals to a base station at the start of a connection or the like. In LTE (Long Term Evolution), an operator needs to allocate RACH Root Sequence (which is referred to hereinafter as a signal sequence) that is a control signal sequence used at that time to each base station sector, which is a communication area of the base station. For example, Non Patent Literature 1 discloses that RACH Root Sequence is composed of 838 sequences.